Tire Monitoring System: Description and Operation
TIRE PRESSURE MONITORINGDESCRIPTION
The Tire Pressure Monitoring (TPM) system monitors air pressure in the four road tires. Pressure in the spare tire is not monitored.
TPM alerts the driver when tire pressure falls below predetermined thresholds.
The TPM system is controlled by the Wireless Control Module (WCM), commonly referred to as the Sentry Key Remote Entry Module (SKREEM).
There is a sensor (transmitter) in each of the vehicle's four road wheels that operates on a 315 MHz radio frequency.
An indicator lamp located in the instrument cluster and, if equipped, the Electronic Vehicle Information Center (EVIC) are used to communicate system information.
OPERATION
The Tire Pressure Monitoring (TPM) system uses radio and sensor technology to monitor tire air pressure levels. Sensors, mounted to each road wheel as part of the valve stem, transmit an RF signal indicating their individual pressure to a receiver located in the Wireless Control Module (WCM), commonly referred to as the Sentry Key Remote Entry Module (SKREEM). These transmissions occur approximately once every minute at speeds over 15 mph (24 km/h). The Tire Pressure Monitoring system remains active even if no tire pressure related message is displayed.
The sensors lay dormant (Park Mode), then wake and start transmitting (Drive Mode) when the vehicle first reaches speeds over 15 mph (24 km/h). Once the wheels stop rotating for a period of approximately 20 minutes, the sensors shut down until again awaken. Although not transmitting as when in Drive Mode, while in Park Mode, the sensors still transmit approximately once every 13 hours to let the receiver know air pressure status at that time. Sensors will also transmit when a pressure change of one psi (seven kPa) or more is detected during that period.
If the system detects that the tire pressure in any road tire is going low, beyond the Low Pressure (lamp) ON threshold, the TPM system will continuously illuminate an indicator lamp. If equipped with the premium TPM system, a message will be displayed in the instrument cluster. The text message will indicate which tire is low and the display will show all current tire pressures, the low tire will be flashing with its pressure value. This message will be displayed for the rest of the ignition cycle, or until the Low Tire pressure condition has been corrected. A chime will sound upon initial detection. Once pressure in the suspect tire raises above the Low Pressure (lamp) OFF Threshold, the lamp will go out and the system returns to normal within approximately two minutes time. If a message center button is pressed, the message is replaced by the new message requested; however, if the Low Tire condition has not been corrected, the Low Tire pressure message will again be displayed.
If a system fault is detected, the indicator lamp will flash on/off for 60 seconds, once every 10 minutes.
TPM THRESHOLD PRESSURES:
